SOLUTION: Lance and Lexi are playing a number-guessing game. Lance asks Lexi to think of a positive number, triple the number, square the result, and then add 7. If Lexi’s answer is 43

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Question 1174349: Lance and Lexi are playing a number-guessing game. Lance asks Lexi to
think of a positive number, triple the number, square the result, and then
add 7. If Lexi’s answer is 43, what was the original number? Use the
concept of inverse function in your solutions.
Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39628)   (Show Source): You can put this solution on YOUR website!
---------------------------------------------------------------
..., think of a positive number, triple the number, square the result, and then
add 7. If Lexi’s answer is 43, ...
------------------------------------------------------------------



If result is y, then





If y=43, then .
Answer by ikleyn(52864)   (Show Source): You can put this solution on YOUR website!
.
Lance and Lexi are playing a number-guessing game. Lance asks Lexi to
think of a positive number, triple the number, square the result, and then
add 7. If Lexi’s answer is 43, what was the original number? Use the
concept of inverse function in your solutions.
~~~~~~~~~~~~~~~~~ 


Moving backward,


(1)  subtract 7 from 43.  Get  43-7 = 36.



(2)  Take the square root of 36.  Get   = 6.

                                  (we accept only POSITIVE square root, according to the condition).



(3)  Divide 6 by 3.   Get   = 2.   


It is the ANSWER.

Do not accept any other answer, since any other number is INCORRECT.

Solved.



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